Diuretic Pregnancy: Spironolactone or its metabolites may cross the placental barrier; feminisation has been observed in male rat fetuses. Use in pregnancy only if the anticipated benefit outweighs the possible hazard to mother and fetus. Metabolites detected in breast milk — if treatment is considered essential, use an alternative method of infant feeding (eMC §4.6).

Spironolactone

Brand names: Aldactone

Used in: Heart Failure Liver Disease & Cirrhosis Hypertension

Spironolactone is a mineralocorticoid-receptor antagonist (a potassium-sparing diuretic) used in heart failure with reduced ejection fraction, resistant hypertension, ascites from liver disease, and primary hyperaldosteronism.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Congestive cardiac failure with oedema: initially 100 mg daily (range 25–200 mg daily)

Route: oral

Frequency: once daily or in divided doses, taken with a meal

Max: Indication-specific ranges up to 400 mg/day (hepatic cirrhosis with ascites, malignant ascites, primary aldosteronism)

UK SPC §4.2. Adults — Congestive cardiac failure with oedema: initial 100 mg daily (single or divided doses), range 25–200 mg daily; maintenance individualised. Severe heart failure (NYHA III–IV, RALES): initiate 25 mg once daily if serum potassium ≤5.0 mEq/L and serum creatinine ≤2.5 mg/dL; if tolerated may increase to 50 mg once daily; if not tolerated reduce to 25 mg every other day. Hepatic cirrhosis with ascites and oedema: 100 mg/day if urinary Na+/K+ ratio >1.0, or 200–400 mg/day if ratio <1.0. Malignant ascites: initially 100–200 mg/day, increased gradually up to 400 mg/day in severe cases. Nephrotic syndrome: 100–200 mg/day. Primary aldosteronism: diagnostic — 400 mg/day (long test 3–4 weeks; short test 4 days); pre-surgery 100–400 mg/day; long-term maintenance at lowest effective dose if unsuitable for surgery. Elderly: start with the lowest dose and titrate up; caution in severe hepatic/renal impairment. Paediatric (per SPC §4.2): initial daily dosage 1–3 mg/kg body weight in divided doses, adjusted to response and tolerance, under paediatric specialist guidance only — verify paediatric dosing against a children's formulary. Administer once daily with a meal. US labelling additionally lists essential hypertension: initial 25–100 mg daily in single or divided doses.

Dose adjustments

Renal

Contraindicated in acute renal insufficiency, significant renal compromise or anuria; use with care in severe renal impairment (eMC). For heart failure, US labelling: eGFR >50 start 25 mg once daily; eGFR 30–50 consider 25 mg every other day owing to hyperkalaemia risk. Monitor serum potassium and creatinine (1 week after initiation/dose increase, then periodically).

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

US labelling (FDA)

Reference — US labelling, may differ from UK

Heart Failure: Initiate treatment at 25 mg once daily ( 2.2 ). Hypertension: Initiate treatment at 25 to 100 mg daily in either single or divided doses ( 2.3 ). Edema: Initiate therapy in a hospital setting and titrate slowly. The recommended initial daily dose is 100 mg in single or divided doses ( 2.4 ). Primary hyperaldosteronism: Initiate treatment at 100 to 400 mg in preparation for surgery. In patients unsuitable for surgery use the lowest effective dosage determined for the individual patient ( 2.5 ). 2.1 General Considerations Spironolactone can be taken with or without food, but should be taken consistently with respect to food [see Clinical Pharmacology (12.3) ] . 2.2 Treatment of …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2025-11-19. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Contraindications

Acute renal insufficiency, significant renal compromise or anuria
Addison's disease
Hyperkalaemia
Hypersensitivity to spironolactone or any excipient
Concomitant use of eplerenone or other potassium-sparing diuretics
Paediatric patients with moderate to severe renal impairment

Side effects

Gynaecomastia (dose- and duration-related; usually reversible); breast pain
Hyperkalaemia; electrolyte imbalance
Menstrual disorder; libido disorder
Nausea; gastrointestinal disorder
Dizziness; malaise

Interactions

Drugs/conditions causing hyperkalaemia — ACE inhibitors, angiotensin II receptor antagonists, other potassium-sparing diuretics, potassium supplements, NSAIDs, heparin/low molecular weight heparin, potassium-containing salt substitutes — risk of severe hyperkalaemia
Trimethoprim/sulfamethoxazole (co-trimoxazole) — may cause clinically relevant hyperkalaemia
Digoxin — spironolactone increases serum digoxin concentration and interferes with certain serum digoxin assays
Lithium — reduced renal clearance and increased risk of lithium toxicity (US labelling §7.2)

Clinical monograph

How it works

It competitively blocks aldosterone at the mineralocorticoid receptor in the distal nephron, promoting sodium and water loss while retaining potassium; in heart failure it also reduces adverse cardiac remodelling.

Prescribing in practice

Hyperkalaemia is the key risk — check renal function and potassium before starting and after initiation or dose increase, and avoid in significant renal impairment or pre-existing hyperkalaemia.
Risk is higher when combined with ACE inhibitors, ARBs, potassium supplements or potassium-sparing drugs.
Gynaecomastia and breast tenderness can occur; eplerenone is an alternative if troublesome.

Monitoring

Monitor potassium and renal function at baseline, after starting or titrating, and periodically; review promptly during intercurrent illness.

Counselling the patient

Avoid potassium-based salt substitutes and over-the-counter potassium supplements.
Report breast tenderness or swelling, or marked tiredness.

Evidence & guidelines

Mineralocorticoid-receptor antagonists improve prognosis in HFrEF (e.g. RALES) and are recommended within guideline-directed therapy (NICE NG106).

Reference: NICE NG106 Chronic HF; RALES Trial NEJM 1999; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Drugs

Furosemide · Diuretic

Pathways